H3N2 California/7 Spreading in Hong Kong
Recombinomics Commentary
March 11, 2005
>> A new strain of flu is spreading in Hong Kong, warned a government health body, but added existing vaccines should offer some protection.
Scientists in Hong Kong recently isolated the H3N2 California virus - previously only found in the United States - in samples here.
Centre for Health Protection principal medical and health officer Teresa Choi urged the public not to panic as the California strain is a minor mutation of the Fujian and Wellington H3N2 viruses - both found in Hong Kong - which are covered by the flu vaccine.
``[All three strains] are close mutations. People who have caught the virus before will have some sort of immunity against the new strain,'' Choi said. She believed the current vaccine can provide some immunity against the new strain, and the number of infections will drop after the March peak flu season.
The center also warned outbreaks of flu infections have surged since last month. It said there were 11 outbreaks so far this month, compared with seven for the whole of last month. <<
Although A/California/7/2004 may have been detected for the first time in Hong Kong, it has been spreading across the globe for many months now. It was originally isolated in Santa Clara, California in September, 2004 but the US began reporting it in January 2005 in antigen characterization tests. Within a few weeks it became the dominant strain in the US. However, it was also seen in Bangkok, Thailand in 2004, and was among the strains that had evolved furthest from Fujian. In the US the most evolved isolate was in Wisconsin in 2004.
In the US, the emergence set off a second wave of infections that resulted in clusters of student deaths last month, but many locations have seen the surge in cases and deaths extend into this month. In Canada there were reports of vaccinated nurses getting the flu. In Russia some schools were closed for the entire month of February.
The vaccine problems in New Zealand can add to the problem. The rapid evolution of H3N2 is taxing vaccine resources. If there is no effective vaccine for the southern hemisphere, the virus could evolve faster.
H3N2 California/7 is quite virulent, and co-circulation in areas that have endemic H5N1 bird flu could provide opportunities for recombination and rapid evolution of more virulent fatal recombinant influenza virus.
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